MULTICAST ROUTING VIA NON-MINIMAL PATHS
A method of routing traffic for multi-cast routing through a node of a network that utilizes loop-free alternative paths is presented. The method includes receiving a join in the node from a second node in the network on a shortest path between the node and the second node; retrieving loop-free alternative paths to the second node; and adding an entry to a multi-cast routing table at the node that is based on a group that includes the shortest path to the second node and the loop-free alternative paths to the second node as cost equivalent paths.
The present application is a continuation of U.S. patent application Ser. No. 14/509,918 filed on Oct. 8, 2014, which is incorporated by reference in its entirety.
TECHNICAL FIELDEmbodiments of the present invention are related to multicast routing and, in particular, to multicast routing using non-minimal paths.
DISCUSSION OF RELATED ARTAs the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option is an information handling system (IHS). An IHS generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes. Because technology and information handling needs and requirements may vary between different applications, IHSs may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in IHSs allow for IHSs to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, IHSs may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
In many systems, typical multicast routing trees are built using a shortest path by sending, for example, protocol independent multicast (PIM) protocol join/prune (J/P) messages. Such messages use the incoming interface on which the join message came rooted at the rendezvous point (RP) or source. This procedure prevents all possible loop-free paths from being used for multicast routing and thereby leads to poor utilization of the network's cross-sectional bandwidth.
Therefore, there is a need to develop a better system for handling multicast routing in a network system.
SUMMARYIn accordance with aspects of the present invention, a method of routing traffic for multi-cast routing through a node of a network. In some embodiments, a method of routing traffic for multi-cast routing through a node of a network includes receiving a join in the node from a second node in the network on a shortest path between the node and the second node; retrieving loop-free alternative paths to the second node; and adding an entry to a multi-cast routing table at the node that is based on a group that includes the shortest path to the second node and the loop-free alternative paths to the second node as cost equivalent paths.
These and other embodiments are further discussed below with respect to the following figures.
In the following description, specific details are set forth describing some embodiments of the present invention. It will be apparent, however, to one skilled in the art that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are meant to be illustrative but not limiting. One skilled in the art may realize other elements that, although not specifically described here, are within the scope and the spirit of this disclosure.
This description and the accompanying drawings that illustrate inventive aspects and embodiments should not be taken as limiting—the claims define the protected invention. Various mechanical, compositional, structural, and operational changes may be made without departing from the spirit and scope of this description and the claims. In some instances, well-known structures and techniques have not been shown or described in detail in order not to obscure the invention.
Additionally, the drawings are not to scale. Relative sizes of components are for illustrative purposes only and do not reflect the actual sizes that may occur in any actual embodiment of the invention. Like numbers in two or more figures represent the same or similar elements.
The singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context indicates otherwise. And, the terms “comprises”, “comprising”, “includes”, and the like specify the presence of stated features, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups. Components described as coupled may be electrically or mechanically directly coupled, or they may be indirectly coupled via one or more intermediate components.
Elements and their associated aspects that are described in detail with reference to one embodiment may, whenever practical, be included in other embodiments in which they are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment and is not described with reference to a second embodiment, the element may nevertheless be claimed as included in the second embodiment.
For purposes of this disclosure, an IHS may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, entertainment, or other purposes. For example, an IHS may be a personal computer, a PDA, a consumer electronic device, a display device or monitor, a network server or storage device, a switch router or other network communication device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The IHS may include memory, one or more processing resources such as a central processing unit (CPU) or hardware or software control logic. Additional components of the IHS may include one or more storage devices, one or more communications ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The IHS may also include one or more buses operable to transmit communications between the various hardware components. In a chassis environment, IHS systems include blades, which are individual systems designed to be inserted into slots on a chassis.
In a network, for example like CLOS or Flattened butterfly among others, there could be multiple unequal paths to reach a given node. A typical multicast is built using the shortest path by sending PIM J/P messages that use the incoming interface on which the join came rooted at the RP or source. Other multicast forwarding protocols, for example like DVMRP, Bidir, TRILL, or internal fabrics within a switch or a router can send similar join messages. This prevents all possible loop free paths to be used for multicast routing and leads to poorer utilization of the network's cross-sectional bandwidth.
According to some embodiments of the present invention, all of the possible paths are used to construct a multicast tree instead of preferring only the shortest path to reach the RP or source. This approach provides better load balancing of multicast traffic for different sets of groups rooted at a single RP. Unicast routing can compute all possible loop-free paths in order to achieve this routing. The PIM protocol can make use of those additional paths to load balance across different multicast group addresses. Traffic can be replicated to the desired node amongst one of the all-possible paths to a given node which further replicates it to its connected receivers. Such an approach is applicable for any kind of network topology, for example CLOS or flattened butterfly.
The joins from a downstream node arrives on the shortest path between the two nodes. Upon receipt of a join, the protocol uses a lookup for its unicast route table DB which provides all possible loop free paths for a given neighbor. For example, if a join came from a node B to node A, then Node A can possibly use on of the loop free alternatives (LFAs) to reach node B rather than using the same shortest path interface to node B on which the join was received. The LFA paths referred here are tunneled paths to that particular node. So the multicast traffic is carried in a unicast tunnel to be delivered to that node, which would terminate and replicate to its local receivers. These unicast tunnels would have been set up already using unicast routing loop free alternative path computation. By this way each multicast group within a RP or source can be load shared across different paths and thereby make efficient use of all available bandwidth for replication. The hardware installs the multicast rout table in such a way that all of the ECMP maps are construed or grouped as one single logical interface. That way, irrespective of the upstream node choosing a particular path, the downstream node can receive the traffic with valid RPF checks passed and replicate the traffic.
Multiple loop-free connections can be made from node A 102 that access each of nodes B 104, C 106, and D 108. For example, the routing from node A 102 to node B 104 through link 110 is the directed routing from node A 102 to node B 104. However, loop-free alternative routings between node A 102 to node B 104 may first be directed through link 116 to node C 106 or through link 118 to node D 108. The loop-free alternative (lfa) routings involve a routings that utilize more than one link.
For example,
By transforming the physical topology to the logical topology illustrated in
Table I below illustrates a unicast routing table for node A 102 using loop-free alternative paths. The routing table illustrates the next-hop for a packet destined from node A 102 to one of nodes B 104, C 106, or D 108. As is illustrated in Table I, the next hop can define either a direct hop to the destination node or a hop to the first node in a loop-free alternative route that ends at the destination node. For example, in the entry where the ingress port is the front-end port of Node A 102 and the destination is node B 104, the next hop may be node B, node C to route on a loop-free alternative path to node B, or to node D to route on a loop-free alternative path to node B.
All routes are replicated for each network dimension as separate virtual routing and forwarding (vrf) routing tables. The total number of forwarding entries into the routing table is equal to the total number of routes times the number of dimensions.
In
In
- A→R3→B;
- A→R3→R1→R4→B;
- A→R3→R2→R4→B;
- A→R3→R1→R5→R2→R4→B;
- A→R3→R1→R6→R2→R4→B;
- A→R3→R2→R5→R1→R4→B;
- A→R3→R2→R6→R1→R4→B.
In general, there are “n” possible loop-free trees that could be formed from router R3 306. Therefore, in accordance with some embodiments of the present invention, different path trees are assigned from router R3 306 that correspond to all unequal paths originating at node A 314 and destined to node B 316. This process occurs for each pair of nodes in the network where traffic is sent (for example a node C, not shown, that is linked to router R6 312).
Loop-free alternative paths can be tunneled paths to the receiving node. In that fashion, multi-cast traffic is carried in a unicast tunnel to be delivered to the receiving node, which terminates and replicates the traffic to its local receivers. Unicast tunnels are setup using a Unicast Routing Loop Free Alternative path computation when the network is first established. Consequently, each multicast group within a RP or source can be load shared across different paths and thereby make efficient use of all available bandwidth for replication.
In some embodiments, the multicast route tables are installed in such a way that all of the equal-cost multi-path routing (ECMP) paths are construed or grouped as one single logical interface. That way, regardless of an upstream node choosing a particular path, the downstream node can receive the traffic with valid reverse-path forwarding (RPF) checks passed and replicate the traffic towards the destination node.
Table II below illustrates a multicast route table at Node A 102 as for the example network shown in
Embodiments of the invention are also applicable to Virtual Link Trunking (VLT). One of the main aspects of VLT is availability of PIM ECMPs at the VLAN level. A single VLT node with multiple upstream VLANs would provide ECMP paths at the VLAN level reach a given RP or source. The current PIM implementation of PIM VLT is restricted to catering to a single VLT VLAN. However, embodiments of the present invention can be applied to VLT networks since the common VLT link is a member of all the upstream VLANs which could be treated as ECMP paths. Regardless of PIM joins being triggered on different VLANs, the underlying hardware would have one common entry to replicate and thereby duplicate. That entry would include loop-free alternative paths.
In some embodiments, in CLOS networks such as that illustrated in
In the preceding specification, various embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set for in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.
Claims
1. A network node comprising:
- a memory; and
- a processor coupled to the memory, the processor being configured to: receive, from another network node, a multicast join message for a multicast group on a shortest path between the network node and the another network node; determine loop-free alternative paths to the another network node; add an entry to a multi-cast routing table stored in the memory, the entry identifying as multicast paths to the another network node for the multicast group the shortest path between the network node and the another network node and each of the loop-free alternative paths as equal cost paths; receive a multicast packet for replication to the multicast group; and replicate the multicast packet to the another network node using any of the shortest path between the network node and the another network node and each of the loop-free alternative paths included in the entry.
2. The network node of claim 1, wherein at least one of the loop-free alternative paths is a tunneled path.
3. The network node of claim 1, wherein the processor is further configured to select a path on which to replicate the multicast packet to provide load balancing among the shortest path between the network node and the another network node and each of the loop-free alternative paths included in the entry.
4. The network node of claim 1, wherein to determine the loop-free alternative paths the processor is further configured to look up the loop-free alternative paths in a unicast routing table.
5. The network node of claim 1, wherein to determine the loop-free alternative paths the processor is further configured to determine trees from a topology between the network node to the another network node.
6. The network node of claim 1, wherein the processor is further configured to perform reverse path forwarding (RPF) checks on the shortest path between the network node and the another network node and each of the loop-free alternative paths included in the entry.
7. The network node of claim 1, wherein the loop-free alternative paths include all of the loop-free alternative paths between the network node and the another network node.
8. A method of routing traffic, comprising:
- receiving, by a first network node from a second network node, a multicast join message for a multicast group on a shortest path between the first network node and the second network node;
- determining, by the first network node, loop-free alternative paths to the second network node;
- adding, by the first network node, an entry to a multi-cast routing table stored in a memory of the first network node, the entry identifying as multicast paths to the second network node for the multicast group the shortest path between the first network node and the second network node and each of the loop-free alternative paths as equal cost paths;
- receiving, by the first network node, a multicast packet for replication to the multicast group; and
- replicating, by the first network node, the multicast packet to the second network node using any of the shortest path between the first network node and the second network node and each of the loop-free alternative paths included in the entry.
9. The method of claim 8, wherein at least one of the loop-free alternative paths is a tunneled path.
10. The method of claim 8, further comprising providing load balancing among the shortest path between the first network node and the second network node and each of the loop-free alternative paths included in the entry.
11. The method of claim 8, wherein determining the loop-free alternative paths comprises looking up the loop-free alternative paths in a unicast routing table.
12. The method of claim 8, wherein determining the loop-free alternative paths comprises determining trees from a topology between the first network node to the second network node.
13. The method of claim 8, further comprising performing reverse path forwarding (RPF) checks on the shortest path between the first network node and the second network node and each of the loop-free alternative paths included in the entry.
14. The method of claim 8, wherein the loop-free alternative paths include all of the loop-free alternative paths between the first network node and the second network node.
15. An information handling system that routes traffic for multi-cast routing, the system comprising:
- a first network node having a memory and a processor coupled to the memory;
- the first network node being configured to: receive, from a second network node, a multicast join message for a multicast group on a shortest path between the first network node and the second network node; determine loop-free alternative paths to the second network node; add an entry to a multi-cast routing table stored in the memory, the entry identifying as multicast paths to the second network node for the multicast group the shortest path between the first network node and the second network node and each of the loop-free alternative paths as equal cost paths; receive a multicast packet for replication to the multicast group; and replicate the multicast packet to the second network node using any of the shortest path between the first network node and the second network node and each of the loop-free alternative paths included in the entry.
16. The system of claim 15, wherein at least one of the loop-free alternative paths is a tunneled path.
17. The system of claim 15, wherein the first network node is further configured to select a path on which to replicate the multicast packet to provide load balancing among the shortest path between the first network node and the second network node and each of the loop-free alternative paths included in the entry.
18. The system of claim 15, wherein to determine the loop-free alternative paths the first network node is further configured to look up the loop-free alternative paths in a unicast routing table.
19. The system of claim 15, wherein to determine the loop-free alternative paths the first network node is further configured to determine trees from a topology between the first network node to the second network node.
20. The system of claim 15, wherein the first network node is further configured to perform reverse path forwarding (RPF) checks on the shortest path between the first network node and the second network node and each of the loop-free alternative paths included in the entry.
Type: Application
Filed: Jan 26, 2017
Publication Date: May 18, 2017
Patent Grant number: 10212068
Inventors: Ramasubramani MAHADEVAN (Chennai), Shivakumar SUNDARAM (Chennai)
Application Number: 15/417,004